This invention relates to three dimensional stereoscopic print images, also known as lenticular stereograms or parallax panoramagrams, and more particularly, to a method and apparatus for increasing the viewing zone of images in lenticular stereograms.
Lenticular stereograms have been used for many years to display a true three-dimensional stereoscopic image without the need for the observer to wear special selection devices which selectively permit the left eye and right eye to see different images. Selection devices are typically eyeglasses that are colored (red/green) or polarized so that a left image and a right image can be viewed from one source. The lenticular stereogram is made by photomechanical reproduction and most commonly used for trading cards, picture postcards, product displays, and the like. By incorporating a cylindrical lenticular screen which has a corduroy-like surface over a properly encoded image print, a stereoscopic three dimensional depth effect may be achieved.
As shown in FIG. 1A, the lenticules 101 have semi-cylindrical surfaces oriented so that their lengths are aligned vertically. The lenticules are in intimate juxtaposition with a print image 102, which contains columns of encoded visual information. Each column of the print image 102 is associated with a particular lenticule, and each column has a series of views ranging from a leftmost to a rightmost perspective. Thus, instead of seeing a single image as in a normal print, the observer of a panoramagram will see perspective images for both the left and right eyes due to the refractive nature of the lenticular surface of the panoramagram. More specifically, because the left eye views the lenticular stereogram from different angles than the right eye, each eye has a different view of the image creating a three dimensional image.
Although the art of making lenticular stereograms is continuing to advance, a number of persistent problems remain which inhibit the medium from becoming more pervasive. In particular, lenticular stereograms have a limited range of points at which they can be viewed without degradation of the three-dimensional image due to the parallax effect. To properly view the entire print or display, all columnar structured images and associated columnar lenticules must be in intimate juxtaposition. The center of an image is typically viewed at a near perpendicular angle, while the left and right edges of the image may be viewed at much more acute angles. The parallax effect occurs at acute viewing angles and creates a lack of precise juxtaposition between the columnar structured image and the associated columnar lenticules. The lack of juxtaposition occurs because at a highly acute angle, the focal point of the lenticule is not properly on the associated print column and an inaccurate columnar image is viewed.
The range of points at which the full and accurate three-dimensional lenticular stereogram image can be seen is known as the xe2x80x9cviewing zone.xe2x80x9d There have been prior art attempts to maximize the viewing zone by reducing the parallax effect. For example, U.S. Pat. No. 5,838,494 discloses a mathematical technique for adjusting the width of the print columns to match the width of the lenticular screen to optimize the viewing zone, but requires obtaining screens with precise lenticule width dimensions. U.S. Pat. No. 5,083,199 requires an air gap to improve the lenticular stereogram viewing zone and it is not clear if paper prints will work with this method. Also, the lenticular screen is imposed on a curved structure with varying lenticule widths which is very difficult to manufacture. The article by E. Sandor et al. entitled xe2x80x9cTechnical Info on PHSColorgrams(copyright)xe2x80x9d (see generally http://www.artn.nwu.edu) discloses increasing the viewing zone of a lenticular stereogram by using print columns which are wider than the width of their corresponding lenticules but does not disclose a method for coordinating the width of the print with the width of the lenticules. Thus, none of these references provides a simple solution for maximizing the viewing zone of a lenticular stereogram.
The present invention sets out to provide a simple method for increasing the viewing zone of a lenticular stereogram.
The present invention is a simple method for increasing the viewing zone of a stereographic image which may be a photographic print, a projected or computer-generated image, or any other type of graphical image. The viewing zone is improved by determining the optimum column width for the image columns of the stereographic image. The optimum column width provides optical alignment for each column with its corresponding lenticule for a specified viewing position. The optimum column width may be determined empirically with a series of test images. Once determined, stereographic images having the optimum column width can be produced using an interdigitation program.
Each test image has a plurality of columns each corresponding to a single lenticule of the lenticular screen. Each column has two single color stripes where the colors are discernible or visually distinct from each other. The colored stripes thus alternate over the complete width of the test image.
The optimum column width is determined by viewing the test image and lenticular screen with a viewing apparatus having a left eye viewing position and a right eye viewing position. When the image appears to be one color when observed from the left eye viewing position and the other color when observed from the right eye viewing position, then the optimum column width has been achieved. The test image having the optimum column width can be determined by viewing a series of such test images having different column widths. Stereographic images can then be produced using the optimum column width and the viewing zone will be maximized when a center column of the stereographic image is aligned with a center lenticule of the lenticular screen.